Nancy Hatch Dupree, who has died aged 89, was an American archivist, writer and champion of Afghanistan’s culture and its people, who defied communists, fundamentalists, warlords and foreign invaders over nearly five decades in Kabul.

Her most important legacy is an archive documenting some of the darkest periods of Afghan history: turbulent years of civil war and Taliban rule that many would happily have let slide into obscurity. The documents are housed in the Afghanistan Centre at Kabul University, established in 2006 and one of the city’s most impressive post-Taliban buildings, inspired by traditional architecture and a reflection of Nancy and her husband Louis Dupree’s love of Afghan culture.

Nancy accompanied Louis on his groundbreaking archaeological and anthropological research as director for 20 years of the American Archaeological Mission to Afghanistan, and went on to set up mobile libraries to reach rural communities and promote literacy. She also wrote guides to Afghanistan that are still among the best introductions to its surviving cultural treasures, and an important record of heritage destroyed by subsequent years of conflict.

A woman of courage, she was part of a tiny group that swung into action in the 1990s when war threatened Kabul, hiding the national museum’s priceless gold collection and then guarding their multimillion-dollar secret in silence for years.

Her determination and formidable willpower were matched by charm, and the Duprees’ parties were as well known as their work. For years in the 1960s and 70s their “five o’clock follies” gathered anyone who was anyone in Kabul – or aspired to be – for cocktails, intrigue and dancing at their home.

Unlike many people who had known a different Afghanistan, though, Nancy managed to celebrate the past without getting stranded among memories or lost in nostalgia. There were stories about dawn rides across beautiful countryside that has since been swallowed by crowded slums, drinking champagne until dawn at the palatial British ambassador’s residence (now the alcohol-free Pakistani embassy).

But there was also hope for the future, embodied by the Afghan students she loved seeing fill the centre’s library and computer rooms when it was completed. “Look to the young people,” she told me, when it was being completed. It was a source of joy and pride that they in turn looked to her.

She was sharp and funny, and one of the many joys of spending time with her in recent years was watching her skewer people who misread her age and increasing frailty and tried to patronise her.

Nancy was born in Cooperstown, New York, to Emily (nee Gilchrist), a former actress, and D Spencer Hatch, an agricultural scientist. She grew up in India, where her father was carrying out rural development work, before attending high school in Mexico and later collecting a degree in Chinese art from Barnard College, New York.

It was an unusual start to a life that would defy all expectations for American women of her era. She first travelled to Kabul in the 60s as a diplomat’s wife, but left her husband, Alan Wolfe (whom she had married in 1952) and embassy life after falling in love with both Louis and Afghanistan itself.

The scandal generated by their affair was heightened when their jilted spouses also got together. Years later, Nancy would lament a perpetual fascination with the scandalous start to her marriage as a liability in ultra-conservative Afghanistan, but never objected to the permanent air of rebellious defiance it gave her. Perhaps her happiest years followed her marriage to Louis in 1966, a period of intense work and travel round a largely peaceful Afghanistan. It came to an abrupt end when the Moscow-backed communist government seized power in 1978, threw her husband in jail, then deported both Duprees.

They lived between the US and the Pakistani border city of Peshawar, where they built up the archive, Nancy worked with refugees, and they dreamed of returning to Kabul, two among the millions of exiles created by Afghanistan’s upheaval.

Louis died of cancer in 1989, but their great love affair animated the rest of Nancy’s life. Preserving his legacy was the driving force in decades of work that would make her as well known as her husband and probably more beloved in Afghanistan. The motto of the foundation she set up to continue their work sums up both her ambition and her modesty: “Rebuilding Afghanistan, one book at a time.”

She was able to return to Kabul after the Russian withdrawal in 1989, travelling back and forth undeterred by the spiralling civil war and later the rise of the Taliban. After the 2001 US invasion brought a temporary calm to the capital, she shipped the precious archive back and started lobbying and fundraising to create a permanent home for it.

In a country awash with money, but cut adrift from its cultural heritage by war and exodus, the Afghanistan Centre is one of very few modern buildings inspired by tradition. Built around a courtyard, filled with light and the fragrance of cedar wood, its outer perimeter is a garden that echoes village streams and pathways.

She hoped that the archive would help with reconstruction and that better understanding of the past might stave off a return to the worst violence. “I am convinced that if you give the Afghan people access to what they need, they themselves will do the work of development,” Nancy once told me. But she was also clear-eyed about Afghanistan’s problems, and had the whole collection digitised so it could survive another slide into chaos, and be accessed abroad.

She never stopped expanding the trove of documents, adding extraordinary finds, such as a box of old photos of the royal family she pulled out once over a casual lunch, an intimate collection somehow teased out of a former confidant.

Her work and unwavering position made her extraordinarily loved in a country generally wary of outsiders, particularly those from countries whose political and military manoeuvring have contributed to more than three decades of war. The former president Hamid Karzai, who had known her for decades, called her a “loving daughter of Afghanistan”; others called her the grandmother of their country. She herself preferred “ancient monument of Afghanistan”.

It was meant as a joke, but her work truly was a monumental tribute, to her beloved husband and the adopted country they both adored.

Nancy is survived by her sister, Jane, and by a niece and nephew, three stepchildren and five stepgrandchildren.

• Nancy Shakuntala Hatch Dupree, conservationist, born 3 October 1927; died 10 September 2017